1. Background Art
The present invention relates to bioassay trays used in laboratories generally and, more particularly, to a novel bioassay tray, or microplate, having rectilinear wells.
2. Background Art
As the sensitivity of the testing protocols for biotechnological and medical research fields has been increased, the volume of reagents and samples has been reduced to microliter quantities. Today, the de facto standard for such fields is a 96-well thermoplastic tray having an array of small wells. The wells, holding up to 300 microliters per well, are conventionally arranged in an 8.times.12 matrix on 9-mm centers.
Originally, the wells were drilled holes in an acrylic block. Later, microplate trays were thermoformed. Now, such plates are injection molded. A common characteristic of all these trays, including those produced by some hundreds of manufacturers thereof world wide is that the wells are round. The bottoms of the wells may be flat, U-shaped, or V-shaped, but the upper portions of all are round.
There are a number of disadvantages to round wells. One is the relatively small volume compared to the available volume of a tray. This means that the volume of media is correspondingly small and the organisms can exhaust their food supply before adequate production byproducts are developed. Conventional round wells on a standard layout cannot simply be made deeper to increase volume, since tray handling and liquid transfer machinery has been built around a de facto height standard. Furthermore, making the wells deeper would decrease the surface area-to-volume ratio, thus decreasing the rate of oxygen transfer to the liquid in the wells.
A further disadvantage of round wells is that, when the contents of the wells are agitated with a reciprocating or oscillatory shaker to promote oxygen transfer to the liquid therein, the cylindrical walls of the wells tend to swirl the media around the inner wall with a minimum of agitation and oxygen transfer.
Another disadvantage of such wells it that there are air gaps between the wells which act as insulators to inhibit heat transfer between wells. Temperature is one of the primary controlling parameters in fermentation processes and it is important that all wells be at the same temperature. This is particularly critical with small volumes. With the insulating air gaps between wells, there can exist a wide temperature gradient between wells, particularly with a change in ambient temperature. For example, when the plate is first put into an incubator, there will be a large temperature gradient between the outer wells and the inner wells which gradient decreases only slowly because of the insulating air gaps.
Accordingly, it is a principal object of the present invention to provide a microplate laboratory tray having a conventional well layout but having increased well volume.
It is a further object of the invention to provide such a tray which allows improved agitation of the contents of the wells.
It is an additional object of the invention to provide such a tray having improved heat transfer between the wells.
It is another object of the invention to provide such a tray that can be used with conventional tray handling and liquid transfer machinery.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.